Whether you need to dress up for dinner on a cruise depends entirely on the cruise line's specific dress code and the "theme" of the evening. In 2026, most mainstream lines like Royal Caribbean, Carnival, and Norwegian have moved toward a "Resort Casual" standard for most nights, which allows for sundresses, slacks, and collared shirts, and often permits "nice" jeans. However, most sailings still feature one or two "Formal Nights" or "Elegant Evenings" where guests are encouraged to wear cocktail dresses, suits, or even tuxedos in the main dining rooms. If you prefer to stay in casual attire like shorts and t-shirts every night, you can always dine at the ship's buffet (Windjammer/Lido) or grab-and-go stations where the dress code is very relaxed. Luxury lines like Cunard or Silversea maintain much stricter "black-tie" requirements for their evening events. To avoid being turned away from the main dining room, it is best to pack at least one "smart" outfit and check the daily newsletter on the cruise app for the specific dress code of the night.